feat: Google (Gemini) provider on the official Gen AI SDK
Phase 4: provider/google on google.golang.org/genai v1.59.0 — lazy cached
client, FunctionResponse tool loop, raw-JSON-schema tools and structured
output, ThinkingLevel reasoning mapping, iter.Pull2 streaming, hermetic
httptest suite via HTTPOptions.BaseURL. Registry wires google + gemini
schemes to the real client; stub machinery deleted (all built-ins real).
ADR-0011; README matrix + CLAUDE.md synced.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
steve
1ca607906d